Structural modeling of the flagellum MS ring protein FliF reveals similarities to the type III secretion system and sporulation complex

Secretion System ◽

Globular Domain ◽

Primary Role ◽

Bacterial Flagellum ◽

The flagellum is a large proteinaceous organelle found at the surface of many bacteria, whose primary role is to allow motility through the rotation of a long extracellular filament. It is an essential virulence factor in many pathogenic species, and is also a priming component in the formation of antibiotic-resistant biofilms. The flagellum consists of the export apparatus and stator in the cytosol; the basal body, spanning the bacterial membrane(s) and periplasm; and the hook-filament, that protrudes away from the bacterial surface. Assembly of the bacterial flagellum is initiated by the formation of the basal body MS ring region, constituted of multiple copies of the protein FliF. Here, I report an analysis of the FliF sequence from various bacterial species, demonstrating that its periplasmic region is composed of a domain homologuous to that of the type III secretion system proteins PrgK, and of a second globular domain that possesses a similar fold to that of the sporulation complex component SpoIIIAG. I also report a structural model for the FliF oligomer, based on knowledge of the PrgK oligomer. These results further emphasize the similarity between the flagellum, T3SS and sporulation complex, and will facilitate further structural studies.

Structural modeling of the flagellum MS ring protein FliF reveals similarities to the type III secretion system and sporulation complex

PeerJ ◽

10.7717/peerj.1718 ◽

2016 ◽

Vol 4 ◽

pp. e1718 ◽

Cited By ~ 14

Author(s):

Julien R. Bergeron

Keyword(s):

Basal Body ◽

Type Iii Secretion ◽

Bacterial Species ◽

Secretion System ◽

Primary Role ◽

Bacterial Surface ◽

Type Iii ◽

C Terminus ◽

Cytosolic Side

The flagellum is a large proteinaceous organelle found at the surface of many bacteria, whose primary role is to allow motility through the rotation of a long extracellular filament. It is an essential virulence factor in many pathogenic species, and is also a priming component in the formation of antibiotic-resistant biofilms. The flagellum consists of the export apparatus on the cytosolic side; the basal body and rotor, spanning the bacterial membrane(s) and periplasm; and the hook-filament, that protrudes away from the bacterial surface. Formation of the basal body MS ring region, constituted of multiple copies of the protein FliF, is one of the initial steps of flagellum assembly. However, the precise architecture of FliF is poorly understood. Here, I report a bioinformatics analysis of the FliF sequence from various bacterial species, suggesting that its periplasmic region is composed of three globular domains. The first two are homologous to that of the type III secretion system injectisome proteins SctJ, and the third possesses a similar fold to that of the sporulation complex component SpoIIIAG. I also describe thatChlamydiapossesses an unusual FliF protein, lacking part of the SctJ homology domain and the SpoIIIAG-like domain, and fused to the rotor component FliG at its C-terminus. Finally, I have combined the sequence analysis of FliF with the EM map of the MS ring, to propose the first atomic model for the FliF oligomer, suggesting that FliF is structurally akin to a fusion of the two injectisome components SctJ and SctD. These results further define the relationship between the flagellum, injectisome and sporulation complex, and will facilitate future structural characterization of the flagellum basal body.

Genetic Analysis of the Salmonella FliE Protein That Forms the Base of the Flagellar Axial Structure

mBio ◽

10.1128/mbio.02392-21 ◽

2021 ◽

Author(s):

Jordan J. Hendriksen ◽

Hee Jung Lee ◽

Alexander J. Bradshaw ◽

Keiichi Namba ◽

Fabienne F. V. Chevance ◽

...

Keyword(s):

Self Assembly ◽

Type Iii Secretion ◽

Adaptor Protein ◽

Ring Structure ◽

Secretion System ◽

Dual Roles ◽

Content Type ◽

Bacterial Flagellum ◽

The FliE component of the bacterial flagellum is the first protein secreted through the flagellar type III secretion system (fT3SS) that is capable of self-assembly into the growing bacterial organelle. The FliE protein plays dual roles in the assembly of the Salmonella flagellum as the final component of the flagellar type III secretion system (fT3SS) and as an adaptor protein that anchors the rod (drive shaft) of the flagellar motor to the membrane-imbedded MS-ring structure.

Broad detection of bacterial type III secretion system and flagellin proteins by the human NAIP/NLRC4 inflammasome

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1710433114 ◽

2017 ◽

Vol 114 (50) ◽

pp. 13242-13247 ◽

Cited By ~ 49

Author(s):

Valeria M. Reyes Ruiz ◽

Jasmine Ramirez ◽

Nawar Naseer ◽

Nicole M. Palacio ◽

Ingharan J. Siddarthan ◽

...

Keyword(s):

Type Iii Secretion ◽

Bacterial Species ◽

Nucleotide Binding ◽

Secretion System ◽

Binding Domain ◽

Leucine Rich Repeat ◽

Nucleotide Binding Domain ◽

Type Iii ◽

Needle Protein

Inflammasomes are cytosolic multiprotein complexes that initiate host defense against bacterial pathogens by activating caspase-1–dependent cytokine secretion and cell death. In mice, specific nucleotide-binding domain, leucine-rich repeat-containing family, apoptosis inhibitory proteins (NAIPs) activate the nucleotide-binding domain, leucine-rich repeat-containing family, CARD domain-containing protein 4 (NLRC4) inflammasome upon sensing components of the type III secretion system (T3SS) and flagellar apparatus. NAIP1 recognizes the T3SS needle protein, NAIP2 recognizes the T3SS inner rod protein, and NAIP5 and NAIP6 recognize flagellin. In contrast, humans encode a single functional NAIP, raising the question of whether human NAIP senses one or multiple bacterial ligands. Previous studies found that human NAIP detects both flagellin and the T3SS needle protein and suggested that the ability to detect both ligands was achieved by multiple isoforms encoded by the single humanNAIPgene. Here, we show that human NAIP also senses theSalmonellaTyphimurium T3SS inner rod protein PrgJ and that T3SS inner rod proteins from multiple bacterial species are also detected. Furthermore, we show that a single human NAIP isoform is capable of sensing the T3SS inner rod, needle, and flagellin. Our findings indicate that, in contrast to murine NAIPs, promiscuous recognition of multiple bacterial ligands is conferred by a single human NAIP.

Hook‐basal body assembly state dictates substrate specificity of the flagellar type‐III secretion system

Molecular Microbiology ◽

10.1111/mmi.14805 ◽

2021 ◽

Author(s):

Alina Guse ◽

Manuel Halte ◽

Svenja Hüsing ◽

Marc Erhardt

Keyword(s):

Substrate Specificity ◽

Basal Body ◽

Type Iii Secretion ◽

Secretion System ◽

The Structures of SctK and SctD from Pseudomonas aeruginosa Reveal the Interface of the Type III Secretion System Basal Body and Sorting Platform

Journal of Molecular Biology ◽

10.1016/j.jmb.2020.10.027 ◽

2020 ◽

Vol 432 (24) ◽

pp. 166693

Author(s):

Meenakumari Muthuramalingam ◽

Sean K. Whittier ◽

Scott Lovell ◽

Kevin P. Battaile ◽

Shoichi Tachiyama ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Basal Body ◽

Type Iii Secretion ◽

Secretion System ◽

Selective Purification of Recombinant Neuroactive Peptides Using the Flagellar Type III Secretion System

mBio ◽

10.1128/mbio.00115-12 ◽

2012 ◽

Vol 3 (3) ◽

Cited By ~ 25

Author(s):

Hanna M. Singer ◽

Marc Erhardt ◽

Andrew M. Steiner ◽

Min-Min Zhang ◽

Doju Yoshikami ◽

...

Keyword(s):

Type Iii Secretion ◽

Recombinant Protein Expression ◽

Surrounding Medium ◽

Secretion System ◽

Bacterial Cells ◽

Content Type ◽

Bacterial Flagellum ◽

Type Iii ◽

Neuroactive Peptides

ABSTRACTThe structure, assembly, and function of the bacterial flagellum involves about 60 different proteins, many of which are selectively secreted via a specific type III secretion system (T3SS) (J. Frye et al., J. Bacteriol. 188:2233–2243, 2006). The T3SS is reported to secrete proteins at rates of up to 10,000 amino acid residues per second. In this work, we showed that the flagellar T3SS ofSalmonella entericaserovar Typhimurium could be manipulated to export recombinant nonflagellar proteins through the flagellum and into the surrounding medium. We translationally fused various neuroactive peptides and proteins from snails, spiders, snakes, sea anemone, and bacteria to the flagellar secretion substrate FlgM. We found that all tested peptides of various sizes were secreted via the bacterial flagellar T3SS. We subsequently purified the recombinant μ-conotoxin SIIIA (rSIIIA) fromConus striatusby affinity chromatography and confirmed that T3SS-derived rSIIIA inhibited mammalian voltage-gated sodium channel NaV1.2 comparably to chemically synthesized SIIIA.IMPORTANCEManipulation of the flagellar secretion system bypasses the problems of inclusion body formation and cellular degradation that occur during conventional recombinant protein expression. This work serves as a proof of principle for the use of engineered bacterial cells for rapid purification of recombinant neuroactive peptides and proteins by exploiting secretion via the well-characterized flagellator type III secretion system.

Robustness and the evolution of length control strategies in the type III secretion system and flagellar hook

10.1101/766733 ◽

2019 ◽

Author(s):

Maulik K. Nariya ◽

Abhishek Mallela ◽

Jack J. Shi ◽

Eric J. Deeds

Keyword(s):

Type Iii Secretion ◽

Average Length ◽

Control Strategies ◽

Bacterial Species ◽

Secretion System ◽

Control Mechanisms ◽

Switching Mechanism ◽

Type Iii ◽

Trade Offs

AbstractBacteria construct many structures, like the flagellar hook and the type III secretion system, that aid in crucial processes such as locomotion and pathogenesis. Experimental work has suggested two competing mechanisms bacteria could use to regulate length in these structures: the “ruler” mechanism and the “substrate switching” mechanism. In this work, we constructed a mathematical model of length control based on the ruler mechanism, and found that the predictions of this model are consistent with experimental data not just for the scaling of the average length with the ruler protein length, but also the variance. Interestingly, we found that the ruler mechanism allows for the evolution of needles with large average lengths without the concomitant large increase in variance that occurs in the substrate switching mechanism. These findings shed new light on the trade-offs that may have lead to the evolution of different length control mechanisms in different bacterial species.

The type III secretion system apparatus determines the intracellular niche of bacterial pathogens

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1520699113 ◽

2016 ◽

Vol 113 (17) ◽

pp. 4794-4799 ◽

Cited By ~ 47

Author(s):

Juan Du ◽

Analise Z. Reeves ◽

Jessica A. Klein ◽

Donna J. Twedt ◽

Leigh A. Knodler ◽

...

Keyword(s):

Epithelial Cells ◽

Type Iii Secretion ◽

Bacterial Pathogens ◽

Bacterial Species ◽

Laboratory Strain ◽

Secretion System ◽

Host Cells ◽

Moderate Degree ◽

Upon entry into host cells, intracellular bacterial pathogens establish a variety of replicative niches. Although some remodel phagosomes, others rapidly escape into the cytosol of infected cells. Little is currently known regarding how professional intracytoplasmic pathogens, includingShigella, mediate phagosomal escape.Shigella,like many other Gram-negative bacterial pathogens, uses a type III secretion system to deliver multiple proteins, referred to as effectors, into host cells. Here, using an innovative reductionist-based approach, we demonstrate that the introduction of a functionalShigellatype III secretion system, but none of its effectors, into a laboratory strain ofEscherichia coliis sufficient to promote the efficient vacuole lysis and escape of the modified bacteria into the cytosol of epithelial cells. This establishes for the first time, to our knowledge, a direct physiologic role for theShigellatype III secretion apparatus (T3SA) in mediating phagosomal escape. Furthermore, although protein components of the T3SA share a moderate degree of structural and functional conservation across bacterial species, we show that vacuole lysis is not a common feature of T3SA, as an effectorless strain ofYersiniaremains confined to phagosomes. Additionally, by exploiting the functional interchangeability of the translocator components of the T3SA ofShigella,Salmonella, andChromobacterium, we demonstrate that a single protein component of the T3SA translocon—ShigellaIpaC,SalmonellaSipC, orChromobacteriumCipC—determines the fate of intracellular pathogens within both epithelial cells and macrophages. Thus, these findings have identified a likely paradigm by which the replicative niche of many intracellular bacterial pathogens is established.

Edwardsiella tarda EscE (Orf13 Protein) Is a Type III Secretion System-Secreted Protein That Is Required for the Injection of Effectors, Secretion of Translocators, and Pathogenesis in Fish

Infection and Immunity ◽

10.1128/iai.00986-15 ◽

2015 ◽

Vol 84 (1) ◽

pp. 2-10 ◽

Cited By ~ 6

Author(s):

Jin Fang Lu ◽

Wei Na Wang ◽

Gai Ling Wang ◽

He Zhang ◽

Ying Zhou ◽

...

Keyword(s):

Type Iii Secretion ◽

Bacterial Species ◽

Lethal Dose ◽

Secretion System ◽

Edwardsiella Tarda ◽

Dependent Manner ◽

Wild Type ◽

Content Type ◽

The type III secretion system (T3SS) ofEdwardsiella tardais crucial for its intracellular survival and pathogenesis in fish. Theorf13gene (escE) ofE. tardais located 84 nucleotides (nt) upstream ofesrCin the T3SS gene cluster. We found that EscE is secreted and translocated in a T3SS-dependent manner and that amino acids 2 to 15 in the N terminus were required for a completely functional T3SS inE. tarda. Deletion ofescEabolished the secretion of T3SS translocators, as well as the secretion and translocation of T3SS effectors, but did not influence their intracellular protein levels inE. tarda. Complementation of theescEmutant with a secretion-incompetent EscE derivative restored the secretion of translocators and effectors. Interestingly, the effectors that were secreted and translocated were positively correlated with the EscE protein level inE. tarda. TheescEmutant was attenuated in the blue gourami fish infection model, as its 50% lethal dose (LD50) increased to 4 times that of the wild type. The survival rate of theescEmutant-strain-infected fish was 69%, which was much higher than that of the fish infected with the wild-type bacteria (6%). Overall, EscE represents a secreted T3SS regulator that controls effector injection and translocator secretion, thus contributing toE. tardapathogenesis in fish. The homology of EscE within the T3SSs of other bacterial species suggests that the mechanism of secretion and translocation control used byE. tardamay be commonly used by other bacterial pathogens.